1. Field of the Invention
The present invention relates to a semiconductor integrated circuit device and, more particularly, to a semiconductor integrated circuit device in which a plurality of signal lines are integrated into a single signal line.
2. Description of the Related Art
Currently, multiplexers are used as semiconductor integrated circuit devices in which a plurality of signal lines are integrated into a single signal line. In the multiplexer, a signal line is selected from the plurality of signal lines, and the selected signal line is electrically connected to the single signal line.
As a multiplexer consisting of a CMOS transistor circuit, a transfer gate type multiplexer as shown in FIG. 1, or a clocked inverter type multiplexer as shown in FIG. 2 has been considered. In either type multiplexer, from selecting signals a, Ba, b, Bb, c, Bc, d, and Bd (the prefix "B" represents an inverted signal), data corresponding to a signal of high level is selected and transmitted to a common node X serving as an output terminal. Note that signals A to D are input data signals, and a signal Q is an output data signal.
In the multiplexer shown in FIG. 1 or 2, however, if the number of to-be-selected data is large, parasitic capacitances such as a junction capacitance and a gate capacitance added to the common node X increase. For this reason, a high-speed data selecting operation to select and output the input data may be impaired.